# Frequently Asked Questions

What is Rat?

Basically, you can think of it as a tool that checks, whether you're source files are carrying proper license headers. Almost any non-trivial organization has a policy for license headers. In the case of the Apache Software Foundation (ASF), this is the ASF Source Header and Copyright Notice Policy.

Where do I find Apache Rat?

Apache Rat is now part of the Apache Creadur project, a home for all sorts of software that helps audit and review software distributions.

Why should I use the Maven plugin to run Apache Rat?

Because it makes running Rat trivial. Basically, you just add the plugin to the `build/plugins` section of your POM and run `mvn apache-rat:check`. Using Rat cannot be simpler.

The apache-rat-plugin creates a report for every subproject. I want a single report for the whole project, which includes the subprojects.

Set the configuration parameter "excludeSubProjects" to false.

Can I use Rat to validate against a custom license header?

See this example to see how.